The reported error messages represent errors originated in the Remote Data Adapter.
After failure and relaunch, the Remote Data Adapter is submitted Subscribe requests for all the items that were subscribed to the old instance.
It seems that the new instance doesn't handle the requests correctly and throws SubscriptionException upon them. The message of the SubscriptionException is then logged by the Proxy Adapter running in the Server.
By the way, the available recovery policies have no impact, as no updates are received.

I confirm that these kinds of errors are not notified to the clients, which only see no updates.
Such metainformation can only be managed at application level. If your Remote Data Adapter intercepted its own SubscriptionExceptions, it might communicate such events, for instance, through a dedicated item.
Anyway, in this case, the main issue seems to be that the Remote Data Adapter, once restarted, fails on the subscriptions.

Nevertheless, stopping and restarting streaming should enforce a new snapshot also the first time, as the snapshot is always kept by Lightstreamer Server.
Can you confirm that
- the items are requested in MERGE mode,
- the interruption is very short,
- the items have already yielded some values at the time of interruption?
Do you observe the updates in the page on a VisualTable or through the event callbacks?